Local IP Access (LIPA) is the ability for an IP-capable mobile device to access a subscriber's Local Area Network (LAN) as well as the Internet directly using the air interface of a femto cell operated by a home base station, such as a Home NodeB (HNB) for Universal Mobile Terrestrial System (UMTS) or a Home evolved-NodeB (HeNB) for Long Term Evolution (LTE).
The ever increasing content available online via email, social networking sites, blogs, RSS feeds, multimedia calls, streaming video and online music, coupled with faster and higher capacity equipment driven by Personal Digital Assistants (PDAs), smart phones and netbooks have led to a boom in the demand for Internet data access using high-speed mobile network infrastructure.
As a result, many operators are faced with bandwidth and network capacity limitations, thus putting a tremendous strain on the existing network infrastructure—hence operators are investing significantly in ramping up existing network capacity on the access network as well as in the core of the network. On the access network side, the introduction of H(e)NB ensures efficient usage of radio spectrum by allowing home users to access the network through the H(e)NB using a local IP backhaul link to the core network. However, this puts an increasing amount of stress on core network nodes since more H(e)NBs connected to the core network means that these nodes have to handle exponentially higher traffic.
Since H(e)NB typically use the ISP's broadband link to provide backhaul connectivity to the core network, it would lessen the stress on core network nodes if IP traffic generated via the HNB were routed through the ISP's network. This would also reduce the number of hops taken by the IP data to reach the destination. Another benefit would be the ability to communicate with other devices within the local subnet without having to go via the mobile operator's core network—hence keeping local traffic truly local.
LIPA uses a Local data GateWay (L-GW) in the home or enterprise network that provides an SGi interface to the IP network. In release 10 of 3rd Generation Partnership Project (3GPP), the L-GW can only and is always collocated with the H(e)NB.
when the H(e)NB has one LIPA connection, one problem in release 10 is the handling of outgoing handovers from the home cell. Indeed, in release 10, the LIPA connections must be torn down at outgoing handover and cannot continue. Necessary means must therefore be found to tear down this connection.
The best existing solution discussed so far in 3GPP is to have the core network, i.e. the Serving Gateway Support Node (SGSN) for UMTS or the Mobility Management Entity (MME) for LTE, trigger the deactivation of the LIPA Packet Data Network (PDN) connection when it is notified of the outgoing handover.
However, this solution is not good enough as it implies that the SGSN or MME is involved in the relocation to be aware of it. Indeed, when the outgoing handover is triggered towards another home cell, the handover signaling may not go via the SGSN or MME which is kept unaware of the move. In this case, the SGSN or MME cannot trigger the deactivation of the LIPA connection.
In addition, even if made aware of the handover, the timing may not be appropriate because the deactivation by the SGSN or MME would take place either during the handover, or after the handover whereas LIPA resources are not allowed at target side.